Opinion: The Genetic Defect Dilemma

Fri, 2009-04-24 11:57

National genetic evaluations have allowed the beef industry to identify those outlier animals that defy genetic antagonisms and excel for a variety of traits. The downside is that we tend to concentrate those bloodlines. The better a genetic pool can be measured, the narrower genetic lines tend to become. With that comes a tendency to increase line breeding, which increases the capability to find and identify genetic defects.

We’re seeing that today in the seedstock industry, with multiple genetic defects having been recently found in the Maine-Anjou, Angus, Red Angus, Shorthorn, Hereford, Holstein and other breeds.

In fact, the Angus breed has identified two genetic defects in the last six months, and a test for a third defect is expected to be released within the next couple of months. The Angus genetic defects have garnered the most publicity and raised the most concern for two reasons. First, Angus holds the breed's dominant position in terms of market share, and, secondly, the fact that both genetic defects traced back to one of the most popular and prominent lines of Angus cattle.

Before the advent of DNA testing, identifying a genetic defect in a line of cattle meant every animal in that line was considered suspect. Many seedstock historians will argue that the dwarfism gene was the catalyst that caused the Hereford breed to fall from its once dominant position in the commercial sector.

Today, however, it’s a much different game. These genetic defects are largely a problem for the purebred sector, as commercial cattlemen have the tools to work around any problem, plus the ability to purchase clean cattle moving forward. From a commercial perspective, only those who have been inbreeding heavily will ever see a problem. One veterinarian commented to me that he will lose hundreds more cattle to scours or respiratory disease than he ever will to these genetic defects.

Of course, possessing the tool of DNA testing to deal with a simple recessive gene certainly changes the playing field and the implications. Ironically, however, it hasn’t removed the difficult decision of how to properly use this technology.

While these genetic defects are virtually guaranteed to never have a significant negative impact at the commercial level, they can devastate certain operations at the seedstock level, both in terms of devaluing breeding stock and eliminating valuable genetic pools.

The Angus breed took a different approach than other breeds in response to this issue. Instead of merely insisting on testing and printing results for full disclosure, then letting breeders and the marketplace assign values, breed officials decided to eliminate the problem more quickly by banning the registration of carrier animals in the future.

Based on good science, arguments can be made for both sides of this issue.

The thing is that our industry is fortunate to have the tools to deal with these genetic defects, as well as others that will occur in the future. But our dilemma is how to most effectively utilize this technology to eliminate problems for the commercial industry and not unnecessarily eliminate large sections of the gene pool.

As is usually the case, technology enables us to deal with a problem, but it is the policy decision on how to utilize that technology that is the real key.